Mapping QTL for ocular component dimensions in chicken

Lead Research Organisation: University of Edinburgh
Department Name: College of Medicine and Veterinary Medic


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Technical Summary

The eye requires exquisite co-ordination of the growth of its component parts to function as an effective optical system. Empirical evidence has shown that ocular component dimensions are under both genetic and environmental control. Two quantitative trait loci (QTL) for eye weight have been mapped in mouse. We propose to extend this work by identifying QTL for the following ocular component dimensions: radius of corneal curvature, anterior chamber depth, lens thickness and vitreous chamber depth. We will use the chicken as a model: chicks have large eyes that facilitate accurate phenotypic measurements, the chicken genome project is nearing completion, and excellent QTL-mapping resources exist for the chicken. In a preliminary study, we found that ocular component dimensions differed markedly between chicks of two different, well-characterised strains (a broiler line and a layer line, respectively). One of the applicants has successfully mapped QTL for body weight from a cross between these two strains. Keratometry, high-resolution A-scan ultrasonography, and eye weight measurements will be carried out on F8 chicks from a broiler x layer advanced intercross line (AIL). DNA samples from these chicks will be genotyped for a panel of 600 informative SNP markers spanning the chicken genome. QTL controlling each trait will be identified using established statistical methods. Fine-mapping of 2-4 of the QTL will be accomplished by genotyping additional markers in regions of interest. As well as providing fundamental insight into the regulation of ocular development, the QTL identified will be targets for modulating eye growth to prevent the progression of refractive errors. Joint with BB/C514482/1


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Description A method for high-throughput, three-dimensional MRI scanning of animal eyes was developed that provides an effective compromise between the competing demands of image resolution, image contrast, scanning time/cost and downstream processing utility (i.e. semi-automated quantification of ocular component dimensions). In collaboration with researchers from the Cardiff University CUBRIC and EMRIC biomedical imaging facilities, the mri3dX software package [1] was enhanced to provide semi-automated quantification of crystalline lens parameters from MRI scans.

The applicants built custom instrumentation and wrote custom software (Visual Basic language) to enable high throughput ocular phenotyping of chickens. Specifically, instrumentation/programs were developed for real-time (i) in vivo high-resolution video-keratometry, (ii) in vivo high-resolution A-scan ultrasonography, and (iii) ex vivo, video-based equatorial diameter measurement.

From a panel of approximately 3000 candidate single nucleotide polymorphisms (SNPs), we have identified a panel of 1667 that are informative (minor allele frequency > 5%) in the Roslin/BBSRC broiler-layer advanced intercross line of chickens. These SNPs will be valuable to other researchers in future QTL mapping experiments using this population, or related broiler-layer crosses.
Exploitation Route The methods can ne used by other researchers and the QTL will facilitate identification of candidate genes for myopia.
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology

Description Fundamental insight into the regulation of ocular development were generated and may be used as targets for modulating eye growth to prevent the progression of refractive errors.
First Year Of Impact 2009
Sector Healthcare
Impact Types Societal